This invention relates to an apparatus for a drum brakes, for mechanically actuatable self-energizing internal shoe-type drum brakes for automotive vehicles. A pair of brake shoes are arranged on a brake carrier plate at a thrust member furnished with tension springs. A mechanical actuating apparatus acting between a pair of brake shoe ends is disposed opposite each other and is prestressed by springs. The mechanical actuating apparatus presses the brake shoes for braking against a brake drum enclosing them, and the drum brake comprises a clearance compensating adjusting apparatus arranged between the brake shoe ends and at least one brake shoe web supporting the brake shoes.
A drum brake with these features is known from the ATE Brake Handbook, Bartsch Verlag, 8th edition, page 135. In that drum brake, a mechanical actuating apparatus provided as an expanding lock is arranged on a brake carrier plate between a first pair of brake shoe ends disposed opposite each other and prestressed by springs. A second pair of the brake shoe ends touches a thrust member at an adjusting apparatus which is comprised of an adjusting nut and an adjusting screw. This adjusting apparatus has the disadvantage that additional manual adjustingly and checking operations both during mounting and during operation are required in order to maintain optimum functioning capability, since manufacturing tolerances of the components and, in particular, the wear of the linings during operation increase the clearance of the brake shoes at an inordinate extent and negatively influence the effective mechanical lever transmission of the expanding lock.
It is, therefore, an object of the present invention to provide a drum brake of the type referred to in which a constant functioning reliability is assured notwithstanding disadvantageous material and design aspects resulting from the manufacture, adjustment and application of the device.